In recent years, compact, high-performance and portable computers, generally called “personal computers,” have come into use in increasing numbers. Now the users can take the personal computers (PCs) everywhere. The user cannot only take the PC everywhere, but also connect the PC to the sub-net at the place where the PC has been brought to and thereby receive various network services. Thus, so-called “mobile computing environment” is now coining into existence.
In the mobile computing environment, the nodes connected to a network are supposed to move. The communication between the nodes must therefore be continuously achieved no matter how and where the nodes are moving. This characteristic of the environment is called “mobile permeability.”
At present it is proposed that mobile permeability be realized on the basis of the specification of IPv6 (Internet Protocol version 6) addresses. There are two protocols for achieving the mobile permeability. They are Mobile IPv6 and VIPonV6.
The use of these two protocols can realize the mobile permeability based on IPv6. It is necessary, however, to use identifiers that are invariable to the moving of the nodes. If such identifiers are used, the packet headers will have a very large size.
Mobile IPv6 or VIPonV6 may be applied in a wireless environment of an extremely narrow band. In this case, the packet headers will inevitably become large in size. This would be particularly a great problem.
All 128 bits of each IPv6 address may be used as a node identifier. If this is the case, the information about the position of the node will be lost completely. Consequently, it will become substantially impossible to control the paths between the sub-nets.